1. Field of the Invention
The present invention relates to an optical disc record medium having a record film on which a guide groove is formed in such a manner that data are recordable and to a production method thereof. In addition, the present invention relates to a recording apparatus that records data on such an optical disc.
2. Description of the Related Art
In an optical disc record medium on which data are capable of being recorded, for example CD-R (Compact Disc-Recordable), DVD-R (Digital Versatile Disc-Recordable) or DVD-RW (ReWritable), a helical guide groove (hereinafter may be referred to as a groove) is formed at a predetermined track pitch. Information is recorded in the guide groove or a portion formed between adjacent paths formed thereof as tracks. In these recordable discs, rotation control information for a spindle motor and address information are recorded by wobbling the groove. In other words, to record data on a record medium, it is necessary to control a spindle motor to rotate at a predetermined rotation rate. The rotation rate is controlled so that a rotation synchronous signal (rotation control information) obtained on the basis of a detection result of wobbling of the groove becomes a predetermined frequency. For example, CLV (Constant Linear Velocity) that keeps a linear velocity constant is used. In addition, an access to a predetermined address is accomplished with address information embedded as wobbles.
FIG. 1 shows an example of wobbling of a groove formed on a disc 100 of related art. In this drawing, a part of the disc 100 of related art is cut out and the shape of the data record surface is shown with a perspective view. In FIG. 1, a guide groove 102 is helically formed on the data record surface of the disc 100. The guide groove 102 is wobbled on the basis of the foregoing rotation control information, address information, and so forth. The guide groove 102 is wobbled on the basis of an FM signal. In other words, a predetermined frequency as the rotation control information is referred to as a carrier frequency. The carrier frequency is frequency-modulated on the basis of address information. The guide groove 102 is wobbled on the basis of a signal obtained as the result of the FM signal. When a drive device side records data on the disc 100, since a tracking error signal contains an frequency modulation (FM) signal on the basis of the wobbling of the guide groove 102, the FM signal is extracted by a band pass filter or the like. The carrier (center frequency) of the FM signal is detected as the rotation control signal. The address information is obtained by demodulating the FM signal itself.
For CD-ROM and MD (Mini Disc), the center frequency of the wobbling is set at for example 22.05 kHz±1 kHz so that it does not adversely affect tracking servo and data reproduction. Likewise, for DVD−R and DVD+R, for example 140.6 kHz and 817.4 kHz are selected as their center frequencies of the wobbling, respectively, so that they do not adversely affect tracking servo and data reproduction.
Thus, the recordable discs of related art have a feature in that desired information such as rotation control information and address information are recorded by wobbling a groove. Information recorded by wobbling a groove can be detected with a push-pull signal. Thus, even if a groove is slightly wobbled, it can be detected with a relatively high sensitivity. Many drive devices are provided with a push-pull signal detection unit so as to detect wobbling of a groove with a high accuracy in such a manner.
Some drive devices for optical disc record mediums may be provided with a mechanism that detects wobbling and determines whether a loaded optical disc is a recordable disc. When the mechanism has determined that the loaded disc be a recordable disc, the mechanism may restrict the operation of the drive device.
The type of a disc has been determined by the determination mechanism mainly for countermeasures against pirated discs. In other words, it can be considered that there is a case of which content of an optical disc record medium sold as a reproduction-only (ROM) disc is illegally copied to recordable discs without permission of the copyright owner and the copied discs are supplied as so-called pirated discs. To prevent such pirated discs from being produced, it is determined whether the type of a disc is recordable depending on whether wobbling has been detected. When the determined result denotes that the disc is a recordable disc and the recorded content is reproduction-only content, assuming that the disc is a pirated disc, the reproduction of content is stopped.
It can be determined whether the content is reproduction-only content depending on whether the content has been encrypted according to CCS (Contents Scrambling System) method.
It is needless to say that such countermeasures against pirated discs have been effective and are important to protect legal rights of copyright owners. However, in recent years, as optical disc record mediums have been widely used, situation for such countermeasures is becoming changed. In other words, legal copyright owners are wanting to intentionally record content to recordable discs and distribute them. It can be said that since reproduction-only ROM discs have a simple structure, resulting in excellent mass producibility and high cost-performance, they are very suitable for mediums for content to be mass-distributed. However, this condition is applied only for the case that the number of discs produced is large. If the number of discs produced is small, the cost for reproduction-only ROM discs may be higher than that for recordable discs with respect to the total cost from production of a disc master to production of final products. Thus, the copyright owner side is desiring to distribute content with recordable discs in the case that mass-distribution of content is not expectable.
However, as can be understood from the foregoing description, wobbles are formed on recordable discs. Thus, if content of a ROM disc has been simply recorded on a recordable disc and distributed therewith, when a user's drive device reproduces the content from the recordable disc, the device detects wobbles, incorrectly determines that the disc be a pirated disc, and stops the reproduction of the content.
As a solution in such a situation, it is thought that rotation control information for a spindle motor, address information, and so forth are recorded without a wobble signal. As a technology that accomplishes such a solution, there is for example Japanese Patent Application Laid-Open No. HEI 9-17033 (patent document 1). Specifically, in the technology of patent document 1, as shown in FIG. 2, the width of a groove is partly enlarged. Information is recorded depending on whether there are enlarged width portions in a groove. In this method, since required information such as address information can be recorded without necessity of wobbling a groove, a drive device provided with such a determination mechanism can prevent a recordable disc on which reproduction-only content has been recorded from being incorrectly determined to be a pirated disc.